Conductivity and thermoelectric power in conducting polypyrrole films

The electrical conductivity and thermoelectric power of films of polypyrrole doped with BF4- have been measured. The electrical conductivity measured in the temperature range 90-300 K follows the variable-range hopping theory proposed by Mott and Davis. However, a variation in the value of the parameter in the exponential expression for conductivity has been observed with film thickness. The magnitude of the thermoelectric power measured in the temperature range 200-300 K is found to be small and p type. The temperature variation in thermoelectric power also obeys the above theory. Some physical parameters such as the density of states at the Fermi level and the hopping distance have been evaluated.